All electrical wires have resistance, that is, frictional losses of power. This resistance converts a small percentage of the power into heat, which then dissipates into the air surrounding the power lines. The greater the current, the greater the loss. This loss is reasonable when the electricity is only moving a few miles. But when utilities start moving it hundreds or thousands of miles, as is the case now, then the losses become enormous.
The balance of electrical power produced versus demand is tenuous at best. The demand for more power is growing as the population increases, while the infrastructure that supplies that power is not able to grow quickly enough to keep up with that demand. The average person is also using more electricity than ever before as electric vehicles become more popular. Energy-draining devices such as air conditioners have certainly become more efficient, but it's not enough to offset the increase in the sheer number of machines people use.
One advantage of a nationwide power grid is the ability to divert electrical power from other areas to cover a temporary outage that storms cause. But the very ability to do so makes the entire grid more vulnerable to damage by enemy forces or weather events. An unforeseen power demand that a generating station causes by going offline can create widespread blackouts and brownouts, as the surrounding areas struggle to maintain power to their local area while also sending power to the stricken area.
Energy consumers can all benefit from assessing their own grid-related vulnerabilities and taking steps to reduce their dependency on the system. These steps can be as simple as a few jugs of stored water and a nonelectric camping stove, as complicated as a full-blown off-grid home power system or just a portable generator for backup power.